Shneiderman’s measurable criteria Chapter 2 Jeff Offutt https://www.cs.gmu.edu/~offutt/ Chapter 2.1, Concept 1 Shneiderman’s measurable criteria

Shneiderman’s Measurable Criteria Time to learn Speed of performance Rate of user errors Retention of skills Subjective satisfaction 26-Feb-19 © Offutt

1. Time to Learn How long it takes to learn how to use an interface With complicated interfaces, learning happens in “plateaus” additional commands Plateau 3 More tasks, more choices, or more speed additional commands Plateau 2 More tasks, more choices, or more speed Plateau 1 Ability to complete at least one simple task initial set of commands 26-Feb-19 © Offutt

2. Speed of Performance Speed of user interface, NOT software Number of characters to type, buttons to press, mouse-clicks, mouse movements, … Speed of performance often directly conflicts with time to learn That is, faster systems are often harder to learn Unix vs. Windows Command lines vs. GUIs Table saws vs. hack saws 26-Feb-19 © Offutt

3. Rate of User Errors A UI can be designed so as to make user mistakes more or less likely Compare C++ with Java Affected by factors such as : Consistency Instructions Logical arrangement of screens Importance depends on criticality of software 26-Feb-19 © Offutt

4. Retention of Skills We quickly forget how to use some user interfaces, but remember others for life Z vs. algebra Airplanes vs. bicycles Affected by how closely the syntax of the operations match our understanding If learning is very fast, retention may be less important 26-Feb-19 © Offutt

5. Subjective Satisfaction How comfortable the users are with the software The other criteria are very analytical, objective, and measurable SS captures other issues that are more specific to individual taste and background Often subjective A little harder to measure 26-Feb-19 © Offutt

Shneiderman’s Measurable Criteria Time to learn Speed of performance Rate of user errors Retention of skills Subjective satisfaction We will spend most of our time on the first 3: Learn, Speed, and Errors 26-Feb-19 © Offutt